1. Flavor Production and Control

2. Off-flavor training © 2017 by Ron Downer Master Brewer

3. Tasting procedure

4. Beer Flavor Wheel

5. Acetaldehyde Green Apple Flavor
The Aldehyde found in highest concentration
Produced by yeast and is the immediate precursor of ethanol
Likely a sign of poorly performing yeast
Can also be caused by bacterial spoilage (Zymomonas)
Some other flavors from this may be apple skin or grassy.
Threshold is around 10 ppm. This is most commonly a symptom of too-young, or “green” beer and should never be detectable.
Threshold in beer: mg/L
Concentration: 45 mg/L
Beer Flavor Wheel #0150
Acetaldehyde

6. Acetic Acid Sour, vinegar flavor
Formed by Acetobacter, which transforms alcohol into acetic acid
Requires oxygen to form
Common in oak-aged beers
Threshold in beer: mg/L
Concentration: 360 mg/L
Beer Flavor Wheel #0910
Acetic Acid

7. Almond Marzipan, Nutty, Nut-Like, or bitter almond
Caused by Benzaldehyde, an aldehyde which is also a primary contributor to a sherry-like flavor
Can be a result of oxidation.
Threshold in beer: 1.0 mg/L
Concentration: 3.0 mg/L
Beer Flavor Wheel #0224
Almond

8. bitter Bitter, Hoppy Isomerized hop alpha acids
Should be clean and pleasant, without harsh, woody, or astringent character
Threshold in beer: mg/L
Concentration: 24 mg/L
Beer Flavor Wheel #1200
bitter

9. Butyric Acid Putrid, baby vomit, rancid butter
Caused by bacterial contamination
Often a marker for Lactobacillus
Develops in spent grain
If you have ever smelled spent grain that has been sitting out overnight in warm weather you know what we are talking about.
Threshold in beer: 3.0 mg/L
Concentration: 7.5 mg/L
Beer Flavor Wheel #0614
Butyric Acid

10. Caprylic acid Goaty, animal, sweat socks, fatty, candle wax
Can be result of microbial contamination or yeast breakdown at maturation
Specific to certain beer styles, particularly long- aged lagers
Threshold in beer: mg/L
Concentration: mg/L
Beer Flavor Wheel #0611
Caprylic acid

11. Contamination Sour and buttery Lactobacillus contamination
Sample is composed of Diacetyl and Acetic Acid
Contamination

12. DMS (Dimethyl sulfide)
Cooked corn or vegetables (parsnip, cabbage); more like tomato juice in dark beers
Acceptable in small amounts in lagers
Created in boil from SMM(s-methyl methionine)
Can also be caused by delay in cooling wort, or by bacterial spoilage (Obesum, bacterium proteus).
Threshold in beer: 𝝁𝒈/𝑳
Concentration: 200 𝝁𝒈/𝑳
Use a long, rolling, open boil. Cool quickly (within 90 minutes after end of boil) before pitching yeast. Do regular checks for possible sites for infection. Use a healthy, vigorous yeast starter.
Beer Flavor Wheel #0732
DMS (Dimethyl sulfide)

13. Buttery, butterscotch, movie popcorn aroma or flavor
Buttery, butterscotch, movie popcorn aroma or flavor. Can manifest itself as a slick mouthfeel.
One of two significant vicinal diketones (VDKs) found in beer.
Caused by not performing a diacetyl rest in lagers, or by separating beer from yeast too early.
Can also be caused by contamination from dirty draft beer lines.
Threshold in beer: mg/L
Concentration: 0.6 mg/L
Beer Flavor Wheel #0620
Diacetyl

14. Earthy Usually perceived as wet, damp, or freshly dug earth.
Not a common taint in beer.
Due to either contamination of water or to storage of packaged beer in a damp area such as a cellar.
Some hop varieties can impart an earthy character to beer.
Threshold in beer: 5.0 𝝁𝒈/𝑳
Concentration: 15 𝝁𝒈/𝑳
#0841 on the Beer Flavor Wheel
Earthy

15. Nail polish remover or solvent
Nail polish remover or solvent. Sometimes evident as an eye-watering sensation.
An important contributor to fruity aromas in beer in small amounts.
In larger amounts may be sign of too-high fermentation temperatures , improper wort aeration, or other yeast stress.
Often found in very high-alcohol beers.
Threshold in beer: mg/L
Concentration: 60 mg/L
Beer Flavor Wheel #0133
Ethyl acetate

16. Ethyl hexanoate Ripe apple, hints of aniseed, licorice.
Present in all beers in varying concentrations.
Becomes an off-flavor at high concentrations.
Produced by yeast during fermentation.
Threshold in beer: 0.2 mg/L
Concentration: 0.6 mg/L
Also known as ethyl caproate.
Beer Flavor Wheel #0132
Ethyl hexanoate

17. geraniol Rose like, floral, or rose water flavor.
Imparted to beer by hops (an important character of hop oil).
Threshold in beer: 𝝁𝒈/𝑳
Concentration: 450 𝝁𝒈/𝑳
Beer flavor wheel #0162
geraniol

18. grainy Husk-like, nut-like, astringent. Sometimes described as “husky”
Can be caused by excessive run-off from lauter tun (trying to get that last bit of sugar from the grain bed), insufficient wort boil, high mash pH, high pH of the sparge liquor, and excessive agitation of the mash.
Beer Flavor Wheel #0310
grainy

19. Hefeweizen Spicy and banana
Composed of Isoamyl Acetate (banana) and 4-Vinyl Guaiacol (clove)
Created by yeast during fermentation
Usually found in specific beer styles
Sample is combination of eugenol (clove) and isoamyl acetate (banana)
Hefeweizen

20. Farm, barnyard
Commonly caused by bacterial infection during fermentation
Indole

21. Isoamyl acetate Banana, bubble gum, peardrop
A fermentation product formed during fatty acid synthesis and then leaks out of yeast cells.
Important contributor to fruity aromas in beer in small amounts
Can be caused by too-high fermentation temperatures, low aeration, or other yeast stress
Beer Flavor Wheel #0131
Isoamyl acetate

22. Isovaleric acid Cheesy, old hops, or unclean sweat socks aroma
Common source is use of old, degraded hops
Organic acid formed during improper storage of hops
Rare in commercial beer
Beer Flavor Wheel # 0613
Isovaleric acid

23. Lactic acid Sour, sour milk
Commonly caused by beer spoilage bacteria (e.g. from Pediococcus, Lactobacillus spp.)
Beer Flavor Wheel # 0920 (sour)
Lactic acid

24. Light-struck Skunky, sulfury, or rubbery aroma
Formed by reaction of a precursor in hop compounds (isohumulones) to blue light
Caused by improper packaging (clear or green bottles)
Beer Flavor Wheel # 0724
Light-struck

25. Mercaptan Sewer-like, drains
Commonly from poor yeast health, autolysis
Beer Flavor Wheel # 0722
Mercaptan

26. Metallic Metal, tin-like, blood, rusty
Present due to water sources, rusty pipes, non- passivated vessels
Can also be caused by excessive recirculation of a DE or sheet filter (more than 20 minutes) which extracts beer soluble iron from the DE
Beer Flavor Wheel #1330
Metallic

27. papery Wet cardboard, stale, oxidized
Product of oxidation, staling, high headspace airs
Also caused by air contact in maturation, filtration, or bright beer tankage
Beer Flavor Wheel #0820
papery

28. Spicy (Eugenol) Cloves, allspice, cinnamon, nutmeg
Eugenol is a strain dependent if dominant and is a trait of wheat beer yeasts
It is a wild yeast defect in other beers
Beer Flavor Wheel #0111
Spicy (Eugenol)

29. Vanilla (vanillin) Custard powder, vanilla essence
A common wood flavor in barrel-aged beers such as Flanders red ales
One of a number of phenolic compounds that can occur in beer
Beer Flavor Wheel #1003
Vanilla (vanillin)